Systems and methods for frequency division duplex communication

ABSTRACT

A method of wireless communication using half duplex frequency division duplex (HD-FDD) comprises, at a wireless communications device, receiving downlink data during a plurality of downlink subframes and transmitting a hybrid automatic repeat request acknowledgement (HARQ-ACK) on an uplink. The HARQ-ACK relates to downlink data received during at least two of the plurality of downlink subframes and the HARQ-ACK is transmitted during one uplink subframe.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.15/666,400, filed Aug. 1, 2017, which claims priority to Great Britainpatent application No. GB 1616610.0, filed on Sep. 30, 2016, thedisclosures of which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present disclosure relates to Frequency Division Duplex (FDD)communication.

BACKGROUND

Long-Term Evolution (LTE) is a wireless communication technologydeveloped by the 3rd Generation Partnership Project (3GPP). LTE definesTime Division Duplex (TDD) and Frequency Division Duplex (FDD) modes ofoperation. LTE also defines two modes of FDD operation: full duplex FDDand Half Duplex FDD (HD-FDD).

Communication between a wireless base station 10 and a user equipment(UE) 20 comprises downlink (DL) transmissions from the base station tothe UE and uplink (UL) transmissions from the UE to the base station.

FIG. 2 schematically shows Full duplex FDD and half duplex FDD. In eachcase there are separate spectral resources for DL and UL communication.In full duplex FDD mode a user equipment (UE) can simultaneouslytransmit and receive using the separate DL and UL resources. Inhalf-duplex FDD mode, the UE cannot receive and transmit simultaneouslyat a given time. The time axis is divided into frames and subframes.During each subframe the UE may receive on the DL or transmit on the UL.

HD-FDD is suited to low-complexity UEs. Because in HD-FDD mode a UE isnot expected to transmit and receive simultaneously, the UE may only becapable of tuning to one frequency band at a time. For example, atransceiver of the UE may only have a single local-oscillator (LO).Re-tuning the LO between DL spectrum and UL spectrum takes some time,and during this re-tuning period the transceiver is not available for DLreception or UL transmission. A half duplex FDD scheme may use a guardperiod to allow a UE to switch retune between a downlink and an uplink.In LTE the terminology for HD-FDD implemented with a single LO is knownas HD-FDD type B. In LTE HD-FDD Type B a re-tuning gap of one subframeis provided. This is called a guard subframe. FIG. 2 shows a guardsubframe for a DL-UL switch and a guard subframe for an UL-DL switch.

There are some further constraints on the achievable downlink data ratein half duplex operation. One constraint is that the UE needs to switchto transmit on the uplink to confirm whether or not it correctlyreceived data on the downlink. In LTE this mechanism is a HybridAutomatic Repeat Request (HARQ) mechanism. The UE transmits a singleHARQ-ACK per downlink transmission. The HARQ-ACK indicates if thedownlink transmission was correctly received (ACK) or if the downlinktransmission was incorrectly received (NACK). There is a fixed timingrelationship between the downlink transmission and the HARQ-ACK replyfrom the UE.

Another constraint is that a UE receives a control message whichschedules a downlink data transmission before receiving the downlinkdata transmission. Both the control message and the downlink datatransmission occur within a group of downlink subframes before the UEswitches to an uplink. This can leave unused periods within a group ofdownlink subframes.

The examples described below are not limited to implementations whichsolve any or all of the disadvantages of known systems.

SUMMARY

There is provided a method of wireless communication using half duplexfrequency division duplex (HD-FDD) comprising, at a wirelesscommunications device: receiving downlink data during a plurality ofdownlink subframes; and transmitting a hybrid automatic repeat requestacknowledgement (HARQ-ACK) on an uplink. The HARQ-ACK relates todownlink data received during at least two of the plurality of downlinksubframes and the HARQ-ACK is transmitted during one uplink subframe.

A timing association between a downlink data subframe and an uplinktransmission subframe for transmitting the HARQ-ACK may be non-uniformfor different downlink data subframes.

Each downlink subframe carrying downlink data may be associated with anHARQ process number. The wireless communications device may store timingdata which indicates a timing association between an HARQ process numberof the downlink data and an uplink transmission subframe fortransmitting the HARQ-ACK.

The timing data may be dependent on at least one of: a number of HARQprocesses; a number of downlink data subframes that a HARQ-ACK relatesto.

The number of HARQ processes in a transmission cycle may be selectedfrom at least one of: 3, 4, 6, 8, 10.

The wireless communications device may receive timing data on a downlinkchannel which indicates a timing association between a downlink datasubframe and an uplink transmission subframe for transmitting theHARQ-ACK.

The timing data may be received as part of a downlink channel indicator(DCI).

Downlink subframes and uplink subframes may be separated by a guardperiod and the method determines a timing of a guard period for adownlink-to-uplink switch by at least one of: determining if the timingdata indicates that the wireless communications device should transmit aHARQ-ACK in a subsequent subframe; determining if the timing dataindicates that the wireless communications device is not expected totransmit data on the uplink.

Uplink subframes and downlink subframes may be separated by a guardperiod and the method determines a timing of a guard period for anuplink-to-downlink switch by at least one of: determining if the timingdata indicates that the wireless communications device is not expectedto transmit a HARQ-ACK on the uplink; determining if the timing dataindicates that the wireless communications device is not expected totransmit data on the uplink.

The HARQ-ACK may comprise an HARQ ACK/NACK indication per HARQ process.

The HARQ-ACK may comprise a single HARQ ACK/NACK indication for theplurality of HARQ processes.

There is provided a method of wireless communication in a system with ahalf duplex frequency division duplexed (HD-FDD) downlink and uplink,the method comprising at a wireless communications device: receiving ascheduling indication of a scheduled downlink data transmission;receiving downlink data during a downlink subframe; wherein thescheduling indication is received before a guard period for adownlink-to-uplink switch and the downlink data is received after aguard period for an uplink-to-downlink switch.

The method may comprise receiving an indication on a downlink channel ofwhether a scheduled downlink data transmission will be delayed untilafter a guard period for an uplink-to-downlink switch.

There may be a first fixed value of scheduling delay between receiving ascheduling indication and receiving a downlink data transmission when ascheduled downlink data transmission will not be delayed until after aguard period for an uplink-to-downlink switch; and there may be a secondfixed value of scheduling delay between receiving a schedulingindication and receiving a downlink data transmission when a scheduleddownlink data transmission will be delayed until after a guard periodfor an uplink-to-downlink switch; and the method may comprise using theindication of whether a scheduled downlink data transmission will bedelayed to determine the scheduling delay.

The indication of whether a scheduled downlink data transmission will bedelayed may be received as a 1-bit parameter.

The indication of whether a scheduled downlink data transmission will bedelayed may be received as part of a multi-bit parameter which alsoindicates a timing association between a downlink data subframe and anuplink transmission subframe for transmitting a hybrid automatic repeatrequest acknowledgement, HARQ-ACK.

The method may comprise: determining a timing of a first guard periodfor a downlink-to-uplink switch; determining a timing of a second guardperiod for an uplink-to-downlink switch; determining a timing of thescheduling indication relative to the determined timing of the firstguard period; and if the timing of the scheduling indication relative tothe determined timing of the first guard period is within a thresholdvalue: determining a transmission time for a delayed scheduled downlinkdata transmission relative to the second guard period.

The method may comprise determining a timing of a guard period for adownlink-to-uplink switch by: determining if the timing data indicatesthat the wireless communications device should transmit a HARQ-ACK in asubsequent subframe; determining if the timing data indicates that thewireless communications device is not expected to transmit data on theuplink.

There is provided a user equipment apparatus configured to perform themethod as described or claimed.

Functionality described in this disclosure are applicable to, but notlimited to, bandwidth reduced low complexity UEs (BL), or UEs inenhanced coverage (CE). Functionality described in this disclosure isapplicable to, but not limited to, Machine Type Communications (MTC).

The methods may be applied to a HD-FDD technology such as LTE HD-FDDType B.

The functionality described here can be implemented in hardware,software executed by a processing apparatus, or by a combination ofhardware and software. The processing apparatus can comprise a computer,a processor, a state machine, a logic array or any other suitableprocessing apparatus. The processing apparatus can be a general-purposeprocessor which executes software to cause the general-purpose processorto perform the required tasks, or the processing apparatus can bededicated to perform the required functions. Another aspect of theinvention provides machine-readable instructions (software) which, whenexecuted by a processor, perform any of the described methods. Themachine-readable instructions may be stored on an electronic memorydevice, hard disk, optical disk or other machine-readable storagemedium. The machine-readable medium can be a non-transitorymachine-readable medium. The term “non-transitory machine-readablemedium” comprises all machine-readable media except for a transitory,propagating signal. The machine-readable instructions can be downloadedto the storage medium via a network connection.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the invention will be described, by way of example, withreference to the following drawings, in which:

FIG. 1 shows a wireless communication system with a downlink and uplinkcommunications;

FIG. 2 shows full duplex FDD and half duplex FDD modes;

FIG. 3 shows an example of a scheduling pattern and HARQ-ACK responsesalready supported by the LTE specification;

FIG. 4 shows an example of a scheduling pattern with bundled HARQ-ACKresponses;

FIGS. 5 to 8 show example tables of timing data;

FIG. 9 shows another example of a scheduling pattern with bundledHARQ-ACK responses;

FIG. 10 shows an example of a scheduling pattern and HARQ-ACK responsesalready supported by the LTE specification;

FIG. 11 shows an example of a known scheduling pattern with delayed DLgrants;

FIG. 12 shows a flow chart of a method performed by a UE;

FIGS. 13 to 17 show scheduling patterns with HARQ-ACK bundling;

FIGS. 18 to 20 show scheduling patterns with delayed DL grants;

FIG. 21 schematically shows example apparatus at a UE.

DETAILED DESCRIPTION

Examples of the present invention are described below by way of exampleonly. These examples represent the best ways of putting the inventioninto practice that are currently known to the Applicant although theyare not the only ways in which this could be achieved. The descriptionsets forth the functions of the example and the sequence of steps forconstructing and operating the example. However, the same or equivalentfunctions and sequences may be accomplished by different examples.

Within the scope of this application it is expressly intended that thevarious aspects, embodiments, examples and alternatives set out in thepreceding paragraphs, in the claims and/or in the following descriptionand drawings, and in particular the individual features thereof, may betaken independently or in any combination. That is, all embodimentsand/or features of any embodiment can be combined in any way and/orcombination, unless such features are incompatible.

Referring again to FIG. 2, an FDD communications system providesseparate spectral resources for DL and UL communication. The spectralresources may comprise a set of frequency subcarriers. The time axis isdivided into frames and subframes. In LTE system, a frame comprises 10subframes numbered #0-#9. In half-duplex FDD mode, during each subframethe UE may receive on the DL or transmit on the UL. A UE may alsorequire time to switch between monitoring the DL and transmitting on theUL. A guard period is provided for the switching. In LTE, Type B HD-FDD,a guard subframe is provided for a DL-UL switch and a guard subframe isprovided for an UL-DL switch.

HARQ-ACK Bundling

For purposes of background explanation, FIG. 3 schematically shows aconventional example of HD-FDD communication. Communication on thedownlink comprises control and data. The UE receives scheduling controlmessages M1, M2, M3 which schedule downlink data transmissions D1, D2,D3 on the data channel(s). Each of the scheduling control messages M1,M2, M3 precedes the downlink data transmission D1, D2, D3 to which itrelates, e.g. M1 precedes D1. The UE sends a separate HARQ-ACK messageon a control channel of the uplink for each of the downlink datatransmissions D1, D2, D3. For example, UL message 1 relates to downlinkdata transmission D1, and so on. There is a fixed timing relationshipbetween the downlink data transmission and the HARQ-ACK. In thisexample, the timing relationship between the downlink data transmissionin subframe n and the associated HARQ-ACK reply is n+4, i.e. 4subframes. The UL HARQ-ACK message 1 is transmitted 4 subframes afterD1, UL HARQ-ACK message 2 is transmitted 4 subframes after D2, and soon.

FIG. 4 shows an example of a modified HD-FDD communication. In thisexample there is a non-uniform timing relationship between downlink datatransmissions and HARQ-ACKs. Similar to FIG. 3, communication on thedownlink comprises control and data. The UE receives scheduling controlmessages M1, M2, M3, M4 which schedule downlink data transmissions D1,D2, D3, D4 on the data channel(s). Each of the scheduling controlmessages M1, M2, M3, M4 precedes the downlink data transmission D1, D2,D3, D4 to which it relates, e.g. M1 precedes D1. Each of the downlinkdata transmissions D1, D2, D3, D4 is associated with an HARQ processnumber. The UE sends a HARQ-ACK acknowledgement on a control channel ofthe uplink for each of the downlink data transmissions D1, D2, D3, D4.The UE combines multiple HARQ-ACKs into a single uplink response sentduring a single uplink subframe. For example, UL acknowledgement message1-2 relates to downlink data transmissions D1 and D2. UL acknowledgementmessage 3-4 relates to downlink data transmissions D3 and D4. This willbe called HARQ-ACK “bundling”. The HARQ-ACK may be transmitted as UplinkControl Information (UCI). The HARQ-ACK may be transmitted on a PhysicalUplink Shared Channel (PUSCH) or a Physical Uplink Control Channel(PUCCH). Scheduling control messages are received on a Physical DownlinkControl Channel for bandwidth reduced low complexity UEs or UEs inenhanced coverage (MPDCCH). Data subframes are received on a PhysicalDownlink Shared Channel (PDSCH).

HARQ-ACK Timing

The timing relationship between the downlink data subframe and theHARQ-ACK is no longer a constant value for each downlink datasubframe/HARQ-ACK pairing. For D1, the timing relationship between thedownlink data subframe D1 in subframe n and the HARQ-ACK 1-2 is n+5,i.e. 5 subframes. For D2, the timing relationship between the downlinkdata subframe D2 and the HARQ-ACK 1-2 is n+4, i.e. 4 subframes. Thiscombining of HARQ-ACK responses can reduce the amount of controlinformation (e.g. UCI) transmitted on the uplink. The non-uniform timingcan allow an increase of the duration of the period before the UE isswitched to the uplink, thereby allowing a higher percentage of time fordownlink data transmission.

There are several possible ways of determining a timing relationshipbetween a downlink data subframe and a subframe to transmit the HARQ-ACKfor that downlink data subframe.

A first way of determining a timing relationship between a downlink datasubframe and a subframe to transmit the HARQ-ACK for that downlink datasubframe is based on the HARQ process number of the downlink datasubframe and stored timing data, such as a look-up table (LUT). In thetable shown in FIG. 5: maxHARQ-Rx is the number of HARQ processes in atransmission cycle; M is the number of downlink subframes (HARQprocesses) associated with a HARQ-ACK response message, i.e. the numberof downlink HARQ-ACK responses bundled together. The table provides atiming association, in terms of a number of subframes (k), correspondingto a DL HARQ process number. In the example shown in FIG. 4,maxHARQ-Rx=4 (there are four HARQ processes in a transmission cycle) andM=2 (each HARQ response carries an acknowledgement for two datatransmissions). The second row of the table provides the timingassociation. For simplicity, it is assumed that D1 corresponds to DLHARQ process number 0, D2 corresponds to DL HARQ process number 1 and soon, but other relationships are possible. Looking up these values in thetable, the HARQ-ACK reply for DL HARQ process number 0 (=D1) has anoffset of 5 subframes, the HARQ-ACK reply for DL HARQ process number 1(=D2) has an offset of 4 subframes.

Stated more formally, the method comprises:

upon detection of a PDSCH with HARQ process number(s) n_(HARQ) _(_)_(ID) within subframe(s) n-k intended for the UE and for which aHARQ-ACK shall be provided; or

upon detection of a MPDCCH indicating downlink Semi-PersistentScheduling (SPS) release for SPS associated with process number(s)n_(HARQ) _(_) _(ID) within subframe(s) n-k intended for the UE and forwhich a HARQ-ACK shall be provided.

The UE transmits the HARQ-ACK response in subframe n using n_(PUCCH)^((l,{tilde over (p)})) as described below. The value of k is given bythe table in FIG. 5. The value of n_(HARQ) _(_) _(ID) is determinedaccording to the HARQ process number field in DCI format 6-1A orassociated with the SPS.

A second way of determining a timing relationship between a downlinkdata subframe and a subframe to transmit the HARQ-ACK for that downlinkdata subframe is based on HARQ process number and stored timing data,such as a look-up table (LUT), similar to the first method above.Additionally, the HARQ-ACK timing can be adjusted dynamically by controlinformation. For example, control information may be received on adownlink control channel with a scheduling message. One example ofimplementing this is to add a 2-bit field to a downlink controlinformation message (DCI), which will be called scheduling and HARQ-ACKdelay in this disclosure. Any other suitable term can be used. Statedmore formally, the method comprises:

upon detection of a PDSCH with HARQ process number(s) n_(HARQ) _(_)_(ID) within subframe(s) n−k+δ intended for the UE and for which aHARQ-ACK shall be provided; or

upon detection of a MPDCCH indicating downlink SPS release for SPSassociated with process number(s) n_(HARQ) _(_) _(ID) within subframe(s)n−k+δ intended for the UE and for which a HARQ-ACK shall be provided.

The UE shall transmit the HARQ-ACK response in subframe n usingn_(PUCCH) ^((l,{tilde over (p)})) as described below. The value of k isgiven by the table in FIG. 6. The value of the parameter δ is determinedusing the table shown in FIG. 7. The table of FIG. 7 maps a 2-bit value“00”, “01”, “10” to a timing adjustment. Essentially, this fine-tunesthe calculation provided by the table of FIG. 6. This method allows someadditional flexibility in scheduling.

A third way of determining a timing relationship between a downlink datasubframe and a subframe to transmit the HARQ-ACK for that downlink datasubframe is based on an explicit value received on a downlink controlchannel. For example, control information may be received on a downlinkcontrol channel with a scheduling message. One example way ofimplementing this is by a 2-bit field in a downlink control informationmessage (DCI), referred to as HARQ-ACK delay field. Stated moreformally, the method comprises:

upon detection of a PDSCH within subframe(s) n−k intended for the UE andfor which a HARQ-ACK shall be provided; or

upon detection of a MPDCCH indicating downlink SPS release withinsubframe(s) n−k intended for the UE and for which a HARQ-ACK shall beprovided.

The UE shall transmit the HARQ-ACK response in subframe n usingn_(PUCCH) ^((l,{tilde over (p)})) as described below, where theparameter k is determined using the table in FIG. 8. This method allowsflexibility in scheduling.

FIG. 9 shows another example of a modified HD-FDD communication. Similarto FIG. 4, there is a non-uniform timing relationship between downlinkdata subframes and uplink acknowledgements. In this example thetransmission cycle comprises 8 scheduling control messages M1-M8 whichschedule downlink data transmissions D1-D8 on the data channel(s). Eachof the scheduling control messages M1-M8 precedes the downlink datatransmission D1-D8 to which it relates. The UE sends a HARQ-ACKacknowledgement on a control channel of the uplink for each of thedownlink data transmissions D1-D8. The UE combines multipleacknowledgements into a single uplink response. UL acknowledgementmessage 1-2 relates to downlink data transmissions D1 and D2; ULacknowledgement message 3-4 relates to downlink data transmissions D3and D4 and so on. This is another example of HARQ-ACK bundling. Thetiming relationship between the downlink data transmission and theHARQ-ACK is non-uniform. For D1, the timing relationship between thedownlink data transmission D1 and the HARQ-ACK 1-2 is n+9, i.e. 9subframes. For D2, the timing relationship between the downlink datatransmission D2 and the HARQ-ACK 1-2 is n+8, i.e. 8 subframes.

One HARQ-ACK is sent in a single UL subframe. The HARQ-ACK may comprisean HARQ ACK/NACK indication per HARQ process/DL subframe, or theHARQ-ACK may comprise a single HARQ ACK/NACK indication for theplurality of HARQ processes/DL subframes. In an example, the HARQ-ACKcan carry 1 or 2 bits of information. If the HARQ-ACK carries 1 bit ofinformation and the HARQ-ACK relates to a bundle of two HARQprocesses/DL subframes, the bit will represent an ACK or NACK value forthe whole bundle of HARQ processes/DL subframes. For example: a value of“1” can indicate all DL transmissions were received OK (ACK); a value of“0” can indicate at least one of the DL transmissions was received witherrors (NACK). In response to sending a 1-bit HARQ-ACK which indicates aNACK, the entire bundle of DL subframes are resent. If the HARQ-ACKcarries 2 bits of information, and the bundle is two DL transmissions,then each of the bits can represent an ACK/NACK for that DLtransmission, e.g. D1 is received OK and D2 is received with errors canbe indicated by a 2-bit HARQ-ACK having the value “10”. In response tosending a 1-bit HARQ-ACK which indicates a NACK, only the corrupted DLtransmission is resent. If a 2-bit HARQ-ACK represents two DLtransmissions, only the DL subframe received in error is resent. It willbe understood that a different number of HARQ-ACK bits may be usedand/or a different number of HARQ processes may be represented. Forexample, if the bundle is four DL transmissions then each of the bits ofthe HARQ-ACK can represent an ACK/NACK for two of the DL transmissions.If the HARQ-ACK is sent on PUCCH, the current formats are used—PUCCHformat 1a to send 1-bit HARQ-ACK and PUCCH format 1b to send 2-bitHARQ-ACK.

It will be understood that, in some situations, the UE will only send aHARQ-ACK relating to one DL subframe. For example, this can occur ifonly one DL subframe is scheduled.

Guard Period Determination

Referring again to the example of FIG. 4, the UE switches between the DLand UL during subframe 6 and the UE switches between the UL and DLduring subframe 10. There are various ways of defining the timing of theguard subframes. One possibility is that the UE can determine the timingof the guard subframes by reference to downlink transmissions andscheduled uplink transmissions. Referring again to the example of FIG.4, the UE receives a scheduling control message M4 during subframe #3which schedules a downlink data transmission D4 during subframe #5. TheUE knows, from stored timing association data (e.g. FIG. 5) that itshould transmit a HARQ-ACK reply on the UL during subframe #7.Therefore, the UE knows that it should switch from DL to the UL duringsubframe #6. Similarly, the UE knows, from stored timing associationdata (e.g. FIG. 5) that it should transmit a HARQ-ACK reply on the ULduring subframe 9. The UE knows this is the last HARQ-ACK reply of thetransmission cycle. Therefore, the UE knows that it should switch fromUL to the DL during subframe #10.

The arrangement is resilient to errors. For example, referring again toFIG. 4, consider that scheduling control messages M1, M2 are notreceived by the UE and therefore the UE does not receive datatransmissions D1, D2. Because D1 and D2 were not received, the UE doesnot need to transmit a HARQ-ACK in subframe #7. Therefore, the UE doesnot switch to the UL during a guard subframe at subframe #6. The UE doesreceive M3, M4 and D3, D4. The UE knows it has to transmit a HARQ-ACK3-4 at subframe 9. Therefore, it switches to the UL during a guardsubframe at subframe #8. In this example the UE recovers quickly fromthe error situation. The HARQ-ACK is still being sent with the correcttiming.

For UE in a half-duplex FDD operation and that is configured withfdd-AckNackFeedbackMode set to ‘bundling’, and for determination of aguard-subframe, the timing of the guard subframe will be decideddynamically based on the HARQ process number of PDSCH transmission thatwas detected by the UE. Stated more formally, the method comprises:

subframe n is a guard-subframe for switching between DL to UL if a UEshall transmit a HARQ-ACK feedback or uplink data (PUSCH transmission)in subframe n+1. subframe n is a guard-subframe for switching between ULto DL if no HARQ-ACK transmission or no PUSCH transmission is expectedby the UE after that subframe.

Uplink transmission on the PUSCH may be initiated by the UE afterreceiving a MPDCCH scheduling message (UL grant), or based onSemi-Persistent Scheduling. In the case of MPDCCH scheduling, then ifthe UL grant is received in subframe n, the uplink transmission PUSCHwill occur in subframe n+4. An uplink transmission during subrame n+4can be either:

(a) a HARQ-ACK transmission following PDSCH in subframe n (or earlierthan n with ACK bundling); or

(b) an UL transmission on PUSCH following MPDCCH UL grant in SF n; or

(c) UL transmission on PUSCH following SPS.

There are several ways of coping with error situations. For example, theUE is not expected to transmit HARQ-ACK if the timing association givenby k+6<4. In case of collision between HARQ-ACK and reception of PDSCH,the PDSCH will be dropped and UE shall transmit the HARQ-ACK.

PUCCH Resource Determination

The UE determines which uplink resource to use to send the HARQ-ACK. Therelevant uplink channel is the Physical Uplink Control Channel (PUCCH).If the UE configured with higher-layer parameter fdd-AckNackFeedbackModeset to ‘bundle’ the UE shall use PUCCH resource n_(PUCCH)^((l,{tilde over (p)})) for transmission of HARQ-ACK in subframe nwhere, if there is a PDSCH transmission indicated by the detection of acorresponding MPDCCH, or for an MPDCCH indicating downlink SPS releasewithin subframe(s) n-k, the UE shall use n_(PUCCH)^((l,{tilde over (p)})) based on the subframe with the smallest value ofk such that HARQ-ACK is sent in subframe n as if there is no HARQ-ACKbundling.

Configuration

The HARQ-ACK bundling mode can be configured at the UE by a wirelessbase station (e.g. eNB) serving the UE. A suitable configurationparameter may be called fdd-AckNackFeedbackMode. The serving eNB mayadditionally configure the UE with a maximum number of DL HARQ processesby higher-layers. A suitable configuration parameter may be calledmaxHARQ-Rx, and may indicate a value between 3 and 10. As shown in FIGS.13 to 20, different bundling schemes may use different maximum number ofHARQ processes.

It is possible to apply HARQ-ACK bundling to LTE HD-FDD Type A. LTEHD-FDD Type A has a shortened guard period for a downlink-to-uplinkswitch and no guard period for an uplink-to-downlink switch. The UE maystill determine when to perform a downlink-to-uplink switch and when toperform a downlink-to-uplink switch, without requiring a guard periodbetween uplink and downlink subframes.

Delayed DL Grant

For purposes of background explanation, FIG. 10 schematically shows aconventional example of HD-FDD communication. Communication on thedownlink comprises control and data. The UE receives scheduling controlmessages M1, M2, M3 which schedule downlink data transmissions D1, D2,D3 on the data channel(s). Each of the scheduling control messages M1,M2, M3 precedes the downlink data transmission D1, D2, D3 to which itrelates, e.g. M1 precedes D1. The UE sends separate HARQ-ACK messages ona control channel of the uplink for each of the downlink datatransmissions D1, D2, D3. A scheduling control message M1, M2, M3 andthe downlink data transmission D1, D2, D3 to which the schedulingmessage relates both occur within the same group of downlinktransmission subframes, before a DL-UL guard subframe. For example, eachof a first group of the scheduling control messages M1, M2, M3 and thedownlink data transmissions D1, D2, D3 occur within the same group ofdownlink transmission subframes 52. Similarly, each of a second group ofthe scheduling control messages M1, M2, M3 and the downlink datatransmissions D1, D2, D3 occur within the same group of downlinktransmission subframes 54. Stated another way, a DL schedulingassignment sent in MPDCCH at subframe n is scheduling a PDSCHtransmission in the same group of downlink transmission subframes. InRel-13 of LTE it was agreed that in order to reduce processingcomplexity for BL/CE UEs, the DL scheduling assignment sent in MPCDCH atsubframe n is scheduling a PDSCH transmission in subframe n+2. A benefitis relaxed processing effort as the time required to complete the MPDCCHdecoding is larger. However, this reduces the downlink data rate becausenot all DL subframes are used for PDSCH transmission. In FIG. 10,subframes #0 and #1 are not used for PDSCH transmission in the firstradio frame. The first DL subframe that can be used is subframe #2 whichwas scheduled by MPDCCH message in subframe #0. Similarly, in the secondradio frame subframes #10 and #11 are not used for PDSCH transmission.

FIG. 11 shows an example of a modified HD-FDD communication. In thisexample there is a non-uniform timing relationship between downlink datatransmissions and uplink acknowledgements. Similar to FIG. 10,communication on the downlink comprises control and data. The UEreceives scheduling control messages M1, M2, M3, M4 which scheduledownlink data transmissions D1, D2, D3, D4 on the data channel(s). Eachof the scheduling control messages M1, M2, M3, M4 precedes the downlinkdata transmission D1, D2, D3, D4 to which it relates, e.g. M1 precedesD1. In this example, scheduling control messages M5, M6 scheduledownlink data transmissions D5, D6 on the data channel(s). Thescheduling control messages M5, M6 occur in a first group of downlinktransmission subframes 61 before a downlink-to-uplink guard subframe 62and the downlink data transmissions D5, D6 occur in a second,subsequent, group of downlink transmission subframes 65 after anuplink-to-downlink guard subframe 64. This will be called delayed DLgrant. The grant at M5, M6 is delayed until the next group of downlinktransmission subframes 65. A guard subframe 62 at subframe 6 allows theUE to switch between DL and UL. A group of uplink subframes 63 occupysubframes #7-9. A guard subframe 64 at subframe #10 allows the UE toswitch between UL and DL. Guard subframes 62, 64 and the group of uplinktransmission subframes 63 separate the scheduling control messages M5,M6 and the downlink data transmissions D5, D6. This arrangement allowsmore (or all) of the downlink subframes to carry data. This can allowhigher efficiency in the downlink subframes and/or higher downlink datarates.

Detecting Delayed DL Grant

The UE may receive an indication, such as via information received on adownlink control channel, when a data transmission is scheduled fortransmission during a subsequent group of downlink transmissionsubframes. An indication, such as a message, or a field or a flag withina message, can explicitly tell the UE that a data transmission willoccur in the next group of downlink transmission subframes. Theindication can be provided as part of the scheduling control message.

According to a first method, upon detecting a downlink assignmentscheduled by MPDCCH, if the value of a field “scheduling and HARQ-ACKdelay” is set to “11”. An example table is shown in FIG. 6. The UE looksup the value of the field “11” and interprets this as a delayed DL grantand sets its scheduling delay to d (=5 in the example table).

According to a second method, an indicator, such as a 1-bit fieldindicator, is included in the DCI message. Upon detecting a downlinkassignment scheduled by MPDCCH, if the value of the field Delayeddownlink assignment indicator is set to 1, the UE will consider this asa delayed DL grant and set its scheduling delay to d. The value of d isknown to the UE.

Timing of Scheduling (MPDCCH) and Downlink Data (PDSCH)

As described above with reference to FIG. 10, in LTE Rel-13 a schedulingmessage on MPDCCH in subframe n schedules a DL subframe on PDSCH insubframe n+2. With delayed DL grant this timing relationship is notkept. The UE is modified to determine a timing association betweenreceiving a scheduling message on a control channel MPDCCH and receivinga DL data subframe on the PDSCH when delayed DL grant is used.

According to a first method, the scheduling delay between receiving ascheduling message on control channel MPDCCH and receiving a DL datasubframe on the PDSCH is determined based on the location of thescheduling message with regard to the guard subframe for a DL-UL switch.If the scheduling message is received one or two subframes before aguard subframe for a DL-UL switch, the UE determines that the grant isdelayed. The UE determines that the DL subframe will occur after a guardsubframe for an UL-DL switch. Referring again to FIG. 11, the UEdetermines that a first guard subframe 62 (DL-UL switch) will occur atsubframe #6 and that a second guard subframe 64 (UL-DL switch) willoccur at subframe #10. The UE determines that the scheduling message M5at subframe #4 is scheduling a delayed DL grant. The UE determines thatthe DL subframe D5 should be transmitted during the subframe after thesecond guard subframe, at subframe #11. The UE determines that thescheduling message M6 at subframe #5 is scheduling a delayed DL grant.The UE determines that the DL subframe D6 should be transmitted twosubframes after the second guard subframe, at subframe #12. The UE candetermine the location of the guard subframes/guard periods using themethod described previously.

Stated more formally: the UE shall, upon detection of a MPDCCH with DCIformat 6-1A intended for the UE in subframe n, decode the correspondingPDSCH in subframe(s) n_tag according to the MPDCCH, where:

n+1 is guard-subframe and the next guard-subframe is n_tag-2; or

n+2 is guard-subframe and the next guard-subframe is n_tag-1

otherwise, n_tag=n+2.

If the time of the guard subframes is fixed (e.g. always subframes #6,#10) the method can operate without a need for the UE to receive anindication of a delayed DL grant. If the time of the guard subframes isnot fixed, but implicitly determined based on HARQ-ACK timing (asdescribed earlier) then the UE can receive an indication when a DL grantis a delayed DL grant. For example, if HARQ-ACK timing is based on HARQprocess number the UE is sent a delayed DL grant indication. Referringto FIG. 11, if M1,M2 are not detected then the UE does not know thatM5,M6 are delayed grants, because it does not know to invoke a guardsubframe at subframe #6. Similarly, if HARQ-ACK timing based on explicitHARQ-ACK delay (method 3)—need for delayed DL grant indication—sameexample here.

According to a second method, the scheduling delay between MPDCCH andPDSCH is fixed to a first value for all non-delayed DL grant pairings(scheduling message, downlink subframe), and is fixed to a second valuefor all delayed DL grant pairings. The UE determines whether there is adelayed DL grant, and therefore determines which timing association touse. A field in the DCI may indicate whether the DL grant is a delayedDL grant or not. For example, all non-delayed DL grants may have a firstscheduling delay value of 2 subframes, and all delayed DL grants mayhave a second scheduling delay value of 7 subframes.

Stated more formally, the method comprises:

upon detection of a MPDCCH with DCI format 6-1A intended for the UE,decodes the corresponding PDSCH in subframe(s) n+k+d according to theMPDCCH, where:

-   -   subframe n is the last subframe in which the MPDCCH is        transmitted and is determined from the starting subframe of        MPDCCH transmission and the DCI subframe repetition number field        in the corresponding DCI; and    -   k=2 is the second BL/CE subframe after subframe n;    -   d is determined based on the scheduling and HARQ-ACK delay field        in the corresponding DCI as described by FIG. 6.

HARQ-ACK Timing

The timing relationship between the downlink data subframe and theHARQ-ACK is no longer a constant value for each downlink datasubframe/HARQ-ACK pairing. Additionally, the timing relationship betweena downlink data subframe/HARQ process and HARQ-ACK may be different atdifferent times during a scheduling sequence. For example, in Figure B2the downlink data D7/D8 can occur in different places with respect toguard subframes. This means the HARQ-ACK timing can vary. There areseveral possible ways of determining a timing relationship between adownlink data subframe and a subframe to transmit the HARQ-ACK for thatdownlink data subframe.

The UE may operate using one of the methods described above under“HARQ-ACK bundling”. The UE may receive control information whichexplicitly informs the UE of a timing association. Alternatively, the UEmay determine a timing association using a table of timing associationinformation based on the HARQ ID, such as FIG. 6, and may additionallyreceive control information which informs the UE of a timing adjustmentto make to the determined relationship.

Guard Period Determination

There are various ways of defining the timing of the guard subframes.One possibility is that the UE can determine the timing of the guardsubframes by reference to downlink transmissions and scheduled uplinktransmissions. Referring again to the example of FIG. 11, the UEreceives a scheduling control message M4 during subframe 3 whichschedules a downlink data transmission D4 during subframe 5. The UE alsoreceives scheduling control messages M5, M6 during subframes 4, 5 whichschedule downlink data transmissions D5, D6 with delayed grant, i.e.during the next group of downlink transmission subframes. The UE knows,from stored timing association data (e.g. FIG. 5) that it shouldtransmit a HARQ-ACK reply 1-2 on the UL during subframe 7. Therefore,the UE knows that it should switch from DL to the UL during subframe 6.Similarly, the UE knows, from the stored timing association data that itshould transmit a HARQ-ACK reply 3-4 on the UL during subframe 9. The UEknows this is the last HARQ-ACK reply of the transmission cycle.Therefore, the UE knows that it should switch from UL to the DL duringsubframe 10. The UE receives downlink data transmissions D5, D6 duringsubframes 11, 12.

It is possible to apply delayed DL grant to LTE HD-FDD Type A. Type Ahas a shortened guard period for a downlink-to-uplink switch and noguard period for an uplink-to-downlink switch. To apply delayed DL grantto Type A, references to “a guard period for a downlink-to-uplinkswitch” may be replaced by “a downlink-to-uplink switch” and referencesto “a guard period for an uplink-to-downlink switch” may be replaced by“an uplink-to-downlink switch”. The UE may still determine when toperform a downlink-to-uplink switch and when to perform adownlink-to-uplink switch, without requiring a guard period betweenuplink and downlink subframes. The method may comprise: receiving ascheduling indication of a scheduled downlink data transmission;receiving downlink data during a downlink subframe; wherein thescheduling indication is received before a downlink-to-uplink switch andthe downlink data is received after an uplink-to-downlink switch.

FIG. 12 shows an example of a method performed by the UE. At block 101the UE receives configuration information, such as a parameterconfiguring at least one of: HARQ-ACK bundling; a number of HARQprocesses. At block 102, the UE determines if it is currently monitoringthe DL. If the UE is currently monitoring the DL it proceeds to block103. The UE receives downlink data. Downlink data received during asubframe carries a HARQ ID. The method may use block 104 or block 105.At block 104, the UE determines a time of a HARQ-ACK response for eachof the received downlink data subframes using stored timing data. Atblock 105 the UE determines a time of a HARQ-ACK response for each ofthe received downlink data subframes using timing data received on adownlink control channel, such as an explicit timing indication carriedin a scheduling message for the downlink transmission. The UE alsodetermines a time of any uplink data subframes on the PUSCH.

At block 106 the UE determines a position of a guard period for a DL-ULswitch based on the times of the HARQ-ACK responses and any uplink(PUSCH) transmissions. At block 107 the UE transmits a HARQ-ACK, orHARQ-ACKs on the uplink. The UE may also transmit uplink data (PUSCH) atthis time. Returning to block 102, if the is not currently monitoringthe DL it must be in an uplink mode. The method proceeds to block 108.At block 108 the UE determines a position of a guard period for an UL-DLswitch based on the times of the HARQ-ACK responses and any uplink(PUSCH) transmissions. After all HARQ-ACK responses (and/or uplinktransmissions) have been sent, the UE switches back to monitor the DL.

FIGS. 13 to 17 show some examples of scheduling patterns with HARQ-ACKbundling. FIG. 13 shows a conventional scheduling pattern with 3 HARQprocesses and no bundling. FIG. 14 shows a scheduling pattern with 4HARQ processes and HARQ-ACK bundling, where each HARQ-ACK responserelates to two DL transmissions. FIG. 15 shows a scheduling pattern with6 HARQ processes and HARQ-ACK bundling, where each HARQ-ACK responserelates to two DL transmissions. FIG. 16 shows a scheduling pattern with8 HARQ processes and HARQ-ACK bundling, where each HARQ-ACK responserelates to two DL transmissions. FIG. 17 shows a scheduling pattern with10 HARQ processes and HARQ-ACK bundling, where each HARQ-ACK responserelates to four DL transmissions (1-4, 5-8) or to two DL transmissions(9-10).

FIGS. 18 to 20 show some examples of scheduling patterns with delayed DLgrants and HARQ-ACK bundling. FIG. 18 shows a scheduling pattern with 6HARQ processes, delayed DL grants and HARQ-ACK bundling, where eachHARQ-ACK response relates to two DL transmissions. FIG. 19 shows ascheduling pattern with 8 HARQ processes, delayed DL grants, andHARQ-ACK bundling, where each HARQ-ACK response relates to two DLtransmissions. FIG. 20 shows a scheduling pattern with 10 HARQprocesses, delayed DL grants, and HARQ-ACK bundling, where each HARQ-ACKresponse relates to four DL transmissions (1-4, 5-8) or to two DLtransmissions (9-10).

FIG. 21 shows apparatus at a UE which may be implemented as any form ofa computing and/or electronic device, and in which embodiments of thesystem and methods described above may be implemented. Processingapparatus 300 comprises one or more processors 301 which may bemicroprocessors, controllers or any other suitable type of processorsfor executing instructions to control the operation of the device. Theprocessor 301 is connected to other components of the device via one ormore buses 306. Processor-executable instructions 303 may be providedusing any computer-readable media, such as memory 302. Theprocessor-executable instructions 303 can comprise instructions forimplementing the functionality of the described methods. The memory 302is of any suitable type such as read-only memory (ROM), random accessmemory (RAM), a storage device of any type such as a magnetic or opticalstorage device. Data 304 used by the processor may be stored in memory302, or in additional memory. Data 304 comprises timing data asdescribed. The processing apparatus 300 comprises a wireless transceiver308. The wireless transceiver 308 may comprise a single LO which iscontrollable to tune to a downlink spectral band or an uplink spectralband.

The above examples are provided by way of example only. The disclosureof this application is not restricted by the specific combination ofsteps shown in the figures, and described herein, but includes anyappropriate subsets or combinations of steps performed in anyappropriate order. Sections of the method may be performed in parallel.

The term ‘user equipment’ (UE) is used herein to refer to any devicewith processing and telecommunication capability such that it canperform the methods and functions according to the examples of thepresent invention. Those skilled in the art will realize that suchprocessing and telecommunication capabilities can be incorporated intomany different devices and therefore the term ‘user equipment’ includesmobile telephones, personal digital assistants, PCs and many otherdevices.

Any range or device value given herein may be extended or alteredwithout losing the effect sought, as will be apparent to the skilledperson.

The skilled person may adapt the examples for use in anytelecommunication network, such as 2G, 3G, 4G, 5G or with any othertelecommunication standard without losing the effect sought.

It will be understood that the benefits and advantages described abovemay relate to one example or may relate to several examples. Theexamples are not limited to those that solve any or all of the statedproblems or those that have any or all of the stated benefits andadvantages.

Any reference to ‘an’ item refers to one or more of those items. Theterm ‘comprising’ is used herein to mean including the method blocks orelements identified, but that such blocks or elements do not comprise anexclusive list and a method or apparatus may contain additional blocksor elements.

The steps of the methods described herein may be carried out in anysuitable order, or simultaneously where appropriate. Additionally,individual blocks may be deleted from any of the methods withoutdeparting from the spirit and scope of the subject matter describedherein. Aspects of any of the examples described above may be combinedwith aspects of any of the other examples described to form furtherexamples without losing the effect sought.

It will be understood that the above description of a preferred examplesis given by way of example only and that various modifications may bemade by those skilled in the art. Although various examples have beendescribed above with a certain degree of particularity, or withreference to one or more individual examples, those skilled in the artcould make numerous alterations to the disclosed examples withoutdeparting from the scope of this invention.

1. A wireless communication method using half duplex frequency divisionduplex, HD-FDD, the method performed by a wireless communication device,comprising: receiving downlink data during a plurality of downlinksubframes; and transmitting a hybrid automatic repeat requestacknowledgement, HARQ-ACK, on an uplink; wherein the wirelesscommunication device receives timing data on a downlink channel whichindicates a timing association between a downlink data subframe and anuplink transmission subframe for transmitting the HARQ-ACK.
 2. Themethod according to claim 1, wherein the HARQ-ACK is generated accordingto at least two of the downlink subframes.
 3. The method according toclaim 1, wherein the timing association between a downlink data subframeand an uplink transmission subframe for transmitting the HARQ-ACK isnon-uniform for different downlink data subframes.
 4. The methodaccording to claim 1, wherein each downlink subframe carrying downlinkdata is associated with an HARQ process number; and the wirelesscommunication device stores a timing data which indicates a timingassociation between an HARQ process number of the downlink data and anuplink transmission subframe for transmitting the HARQ-ACK.
 5. Themethod according to claim 4, wherein the timing data is dependent on atleast one of a number of HARQ processes and a number of downlink datasubframes in associated with the HARQ-ACK.
 6. The method according toclaim 1 wherein a number of HARQ processes in a transmission cycle isselected from at least one of: 3, 4, 6, 8 and
 10. 7. The methodaccording to claim 1, wherein the downlink subframes and uplinksubframes are separated by a guard period and the method determines atiming of a guard period for a downlink-to-uplink switch by at least oneof: determining if the timing data indicates that the wirelesscommunication device should transmit a HARQ-ACK in a subsequentsubframe; and determining if the timing data indicates that the wirelesscommunication device is not expected to transmit data on the uplink. 8.The method according to claim 1, wherein uplink subframes and downlinksubframes are separated by a guard period and the method determines atiming of a guard period for an uplink-to-downlink switch by at leastone of: determining if the timing data indicates that the wirelesscommunication device is not expected to transmit a HARQ-ACK on theuplink; and determining if the timing data indicates that the wirelesscommunication device is not expected to transmit data on the uplink. 9.The method according to claim 1, wherein the HARQ-ACK comprises an HARQACK/NACK indication.
 10. The method according to claim 1, wherein theHARQ-ACK comprises a single HARQ ACK/NACK indication for a plurality ofHARQ processes.
 11. A wireless communication method using half duplexfrequency division duplex, HD-FDD, the method performed by a wirelessbase station, comprising transmitting downlink data during a pluralityof downlink subframes to a mobile communication device; and receiving ahybrid automatic repeat request acknowledgement, HARQ-ACK, from themobile communication device; wherein the wireless base station transmitstiming data on a downlink channel which indicates a timing associationbetween a downlink data subframe and an uplink transmission subframe fortransmitting the HARQ-ACK.
 12. The method according to claim 1, whereinthe HARQ-ACK is generated according to at least two of the downlinksubframes.